Plasma CVD system

ABSTRACT

A plasma CVD system has a reactor which can be evacuated, a substrate holding means in the reactor, a material gas feed means for feeding into the reactor a material gas for plasma CVD, a high-frequency power supply means for supplying an electrode high-frequency power of 30 MHz to 600 MHz, generated by a high-frequency power source, and means for exhausting gas remaining in the reactor after the reaction. The high-frequency power is supplied to produce a plasma across a substrate in the reactor to form a deposited film on the substrate, and the phase of reflected power is adjusted on the electrode at a side opposite the feeding point. High-quality deposited films having very uniform film thickness and homogeneous film quality can be formed at a high rate and stably on large-area substrates having any shapes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a plasma CVD (chemical vapor deposition)process and a plasma CVD system which make use of high-frequency powerand are usable in the manufacture of semiconductor devices,electrophotographic photosensitive member devices, image-inputting linesensors, flat-panel display devices, image pickup devices, photovoltaicdevices and so forth.

2. Related Background Art

In recent years, in the process of producing semiconductor devices andthe like, plasma CVD systems and plasma CVD processes have been put intopractical use in an industrial scale. In particular, plasma CVD systemsmaking use of a high-frequency power of 13.56 MHz are in wide usebecause processing can be carried out regardless of whether substratematerials and deposited-film materials are conductors or insulators.

As an example of conventional plasma-producing high-frequency electrodesand plasma CVD systems and processes making use of such electrodes, aparallel-plate type system will be described with reference to FIG. 1.In a reactor 101, a high-frequency electrode 103 is provided via aninsulating high-frequency electrode support base 102.

The high-frequency electrode 103 is a flat plate provided in parallel toan opposing electrode 105, and plasma is caused to take place by the aidof an electric field determined by electrostatic capacitance exhibitedbetween the electrodes. Once plasma has taken place, a plasma regionwhich is substantially a conductor and a sheath which acts chiefly as acapacitor in an equivalent manner between the plasma and the bothelectrodes or reactor wall are formed between the electrodes to providean impedance greatly different from that before the plasma takes place.

Around the high-frequency electrode 103, an earth shield 104 is providedso that any discharge may not occur between the side of thehigh-frequency electrode 103 and the wall of the reactor 101. To thehigh-frequency electrode 103, a high-frequency power source 111 isconnected through a high-frequency power supply wire 110.

A flat-plate film-forming substrate 106 on which plasma CVD is carriedout is attached to the opposing electrode 105 provided in parallel tothe high-frequency electrode 103, and the substrate 106 to be processedis kept at a desired temperature by a substrate temperature controlmeans (not shown).

Plasma CVD using this system is carried out in the following way. Afterthe inside of the reactor 101 is evacuated to a high vacuum by anevacuation means 107, reaction gases are fed into the reactor 101through a gas feed means 108, and its inside is kept at a predeterminedpressure. A high-frequency power is supplied from the high-frequencypower source 111 to the high-frequency electrode 103 to cause a plasmato take place across the high-frequency electrode and the opposingelectrode.

Thus, the reaction gases are decomposed and excited by plasma to form adeposited film on the film-forming substrate 106. As the high-frequencypower, it is common to use a high-frequency power of 13.56 MHz. Use ofsuch a discharge frequency of 13.56 MHz makes it relatively easy tocontrol discharge conditions and brings about an advantage that the filmformed can have a good film quality, but may result in a low gasutilization efficiency and a relatively small deposited-film formationrate.

Taking account of these points, studies are made on plasma CVD carriedout at a high-frequency power having a frequency of about 25 to 150 MHz.For example, Plasma Chemistry and Plasma Processing, Vol. 7, No. 3,1987, pp.267-273 (hereinafter “publication 1”) discloses that a materialgas (silane gas) is decomposed by a high-frequency power having afrequency of about 25 to 150 MHz, using a parallel-plate type glowdischarge decomposition system.

Stated specifically, the publication 1 discloses that, in the formationof a-Si films at frequencies changed within the range of from 25 MHz to150 MHz, film deposition rate reaches a maximum of 2.1 nm/sec when 70MHz is used, and this is a formation rate about 5 to 8 times that in theplasma CVD carried out at 13.56 MHz, and that a-Si film defect density,optical band gap and conductivity are not so much affected by excitationfrequencies.

The publication 1 shows an example of a plasma CVD system suited for theprocessing of flat substrates of a laboratory scale. As for an exampleof a plasma CVD system suited for the formation of deposited films onfilm-forming substrates of a large industrial scale (e.g., cylindricalsubstrates), it is disclosed in, e.g., U.S. Pat. No. 5,540,781(hereinafter “publication 2”).

This publication 2 discloses a plasma CVD process and a plasma CVDsystem which make use of a high-frequency power of what is called VHFband, having a frequency of from 60 MHz to 300 MHz. The plasma CVDsystem as disclosed in the publication 2 will be described withreference to FIG. 2.

The plasma CVD system shown in FIG. 2 is the VHF plasma CVD systemdisclosed in the publication 2.

In FIG. 2, reference numeral 200 denotes a reactor. The reactor 200 hasa base plate 201, insulating members 202A, cathode electrodes 203C,insulating members 221B, cathode electrodes 203B, insulating members221A, cathode electrodes 203A, insulating members 202B and a top cover215.

Reference numeral 205A denotes a substrate holder, which has a heatercolumn 205A′ inside. Reference numeral 205A″ denotes a substrate heaterattached to the heater column 205A′. Reference numeral 206 denotes acylindrical film-forming substrate provided on the substrate holder205A. Reference numeral 205B denotes an auxiliary holding member for thecylindrical film-forming substrate 206. The substrate holder 205A has atits bottom a rotating mechanism (not shown) connected to a motor and isso designed as to be optionally rotatable. Reference numeral 207 denotesan exhaust pipe having an exhaust valve, and the exhaust pipecommunicates with an exhaust mechanism 207′ having a vacuum pump.Reference numeral 208 denotes a material gas feed assemblage constitutedof gas cylinders, mass-flow controllers, valves and so forth. Thematerial gas feed assemblage 208 is connected to gas release pipes 216having a plurality of gas release holes, through a gas feed pipe 217.Material gases are fed into the reactor through the plurality of gasrelease holes of the gas release pipes 216. Reference numeral 211denotes a high-frequency power source, and a high-frequency powergenerated here is supplied to the cathode electrodes 203 (203A to 203C)through a high-frequency power supply wire 218 and matching circuits 209(209A to 209C). In the plasma CVD system shown in FIG. 2, the cathodeelectrodes are so constituted as to be divided electrically into threeelectrodes 203A, 203B and 203C in the axial direction of the cylindricalfilm-forming substrate. The high-frequency power generated in thehigh-frequency power source 211 is divided into three parts by ahigh-frequency power dividing means (distributor) 220, and then suppliedto the cathode electrodes 203A, 203B and 203C through matching circuits209A, 209B and 209C, respectively.

The publication 2 also describes a plasma CVD process carried out usingthe plasma CVD system shown in FIG. 2.

That is, in the system shown in FIG. 2, the cylindrical film-formingsubstrate 206 is set to the substrate holder 205, and thereafter theinside of the reactor 200 is evacuated by the operation of the exhaustmechanism 207′ to evacuate the inside of the reactor to have apredetermined pressure. Then, the heater 205A″ is electrified to heatthe substrate 206 so as to be kept at a desired temperature.

Next, material gases are fed into the reactor 200 from the material gasfeed assemblage 208 through the gas feed pipe 217 and gas release pipes216, and the inside of the reactor is adjusted to a desired pressure. Inthis state, a high-frequency power having a frequency in the range offrom 60 MHz to 300 MHz is generated by the high-frequency power source211. The high-frequency power is divided into three parts in thehigh-frequency power distributor 220, and then supplied to the cathodeelectrodes 203A, 203B and 203C through the matching circuits 209A, 209Band 209C, respectively. Thus, in the space defined by the cylindricalfilm-forming substrate 206 and the cathode electrodes, the materialgases are decomposed by high-frequency energy to produce active species,so that a deposited film is formed on the cylindrical film-formingsubstrate 206.

The publication 2 states that, since the cylindrical cathode electrodeis divided in the plasma CVD system making use of the high-frequencypower having a frequency in the range of from 60 MHz to 300 MHz asstated above, a highly uniform deposited film can be formed on alarge-area cylindrical film-forming substrate while maintaining the highfilm deposition rate that is an advantage of the VHF regionhigh-frequency plasma CVD.

However, the film formation using the high-frequency power having afrequency of from 25 to 150 MHz in the parallel-plate type systemdisclosed in the publication 1 is carrie out in a laboratory scale, andalso the publication does not refer at all to whether or not such aneffect can be expected in the formation of large-area films. In general,the higher the excitation frequency is, the more remarkable theinfluence of standing waves produced on a high-frequency electrode is,where, especially on flat electrodes, two-dimensional complicatedstanding waves may occur. Hence, it is foreseen that it will bedifficult to form large-area films uniformly.

In the plasma CVD process and plasma CVD system disclosed in the priorart publication 2, it can be expected that deposited films are formed ata high deposition rate and in a high uniformity when large-areadeposited films are formed in a cylindrical form. However, it isforeseen that a plurality of feeding points will be required on onecathode to make the system complicated and also that it will bedifficult to make adaptation to flat substrates.

SUMMARY OF THE INVENTION

Objects of the present invention are to solve the problems the prior arthas had, and to provide a plasma CVD process and a plasma CVD system bywhich high-quality deposited films having a very uniform film thicknessand a homogeneous film quality can be formed at a high rate and stablyon large-area substrates having any shapes, to obtain semiconductordevices in a good efficiency.

The present invention provides a plasma CVD system comprising a reactorthe inside of which can be evacuated, a substrate holding means providedin the reactor, a material gas feed means for feeding into the reactor amaterial gas for plasma CVD, a high-frequency power supply means forsupplying to a plasma-producing high-frequency electrode ahigh-frequency power having an oscillation frequency in the range offrom 30 MHz to 600 MHz, generated by a high-frequency power source, andan exhaust means for exhausting a gas remaining in the reactor after thereaction; the high-frequency power generated in the high-frequency powersource being supplied to the plasma-producing high-frequency electrodeto cause a plasma to take place across a substrate held by the substrateholding means and the plasma-producing high-frequency electrode to forma deposited film on the substrate; wherein,

a phase-adjusting circuit for adjusting the phase of reflected power isconnected to the plasma-producing high-frequency electrode at its endportion on the opposite side of a feeding point at which thehigh-frequency power is supplied to the plasma-producing high-frequencyelectrode.

The present invention also provides a plasma CVD process comprising thesteps of feeding a material gas for film formation into a reactor theinside of which is kept evacuated, and decomposing the material gas intoplasma by the aid of a high-frequency power having a frequency in therange of from 30 MHz to 600 MHz, to form a deposited film on a substrateprovided inside the reactor, wherein;

a plurality of rod-like or plate-like conductive plasma-producinghigh-frequency electrodes are used to produce plasma by the aid of thehigh-frequency power, and the phase of reflected power is adjusted at apart of each plasma-producing high-frequency electrode on the oppositeside of its feeding point, to produce a plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional view showing an example of aplasma CVD system having parallel-plate electrodes.

FIG. 2 is a diagrammatic cross-sectional view showing an example of aplasma CVD system which can form a deposited film on a cylindricalsubstrate.

FIGS. 3A and 3B each schematically illustrate an example of how power issupplied to a plasma-producing high-frequency electrode and aphase-adjusting circuit is connected.

FIG. 4, FIG. 5, FIG. 6, FIG. 7 and FIG. 8 are each diagrammaticcross-sectional view illustrating a preferred example of a plasma CVDsystem having phase-adjusting circuits.

FIG. 9 and FIG. 10 are each diagrammatic perspective view illustrating apreferred example of a plasma CVD system having phase-adjustingcircuits.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present invention, the phase of reflected power on the oppositeside of the feeding point of a high-frequency electrode is adjusted sothat the above objects of the present invention can be achieved. This isbased on the following results of studies made by the present inventors.

As a result of extensive studies, the present inventors have reached afinding that setting the high-frequency power to a frequency of 30 MHzor above enables discharge to take place in a high-vacuum region thatmay hardly cause polymerization reaction in the gaseous phase, canachieve always superior film properties and brings about an improvementalso in deposition rate compared with the case of 13.56 MHz, but thereis still a problem in the stability of discharge in the high-vacuumregion and may result in poor distribution of film quality anddeposition rate.

Accordingly, the present inventors further made extensive studies toelucidate the reason why the film quality lowers locally and depositionrate decreases when the high-frequency power is set to a frequency of 30MHz or above. As the result, it has been found that there is a strongcorrelation between plasma potential and the local lowering of filmquality and also a strong correlation between electron density in plasmaand the deposition rate. More specifically, as a result of measurementof plasma potential in the axial direction of a cylindrical film-formingsubstrate by the Langmuir probe method, a decrease in plasma potentialwas seen at the part corresponding to the position where the filmquality lowered locally.

From these results of studies, it is presumed that the poor distributionof film quality and deposition rate is caused by standing waves producedon the high-frequency electrode and by attenuation of high-frequencypower on the high-frequency electrode. In general, when a high-frequencypower is applied across a high-frequency electrode and an opposingelectrode to produce plasma, unnegligible standing waves may be producedon the electrodes because of the relationship between the frequency ofhigh-frequency power applied to the electrodes and the size of theelectrodes. More specifically, standing waves tend to be produced whenthe high-frequency power has a high frequency or when the high-frequencyelectrode has a large area. If the standing waves are great, theelectric field distribution in the high-frequency electrode may becomepoor to disturb plasma distribution such as plasma density, plasmapotential and electron temperature between the electrodes to adverselyaffect the quality of films formed by plasma CVD. In the experimentmentioned above, it is considered that reflected waves have beenproduced on the high-frequency electrode at an end of the high-frequencyelectrode and their interference with incident waves has caused thestanding waves that may affect film quality and deposition rate at afrequency of 30 MHz or above. In particular, it is considered that theelectric field is so weak at the position of nodes of standing waves asto cause a decrease in local plasma potential to lower film qualitylocally.

The present invention has been accomplished on the basis of the aboveresults of studies. The present invention will be described below withreference to the accompanying drawings.

First, the plasma-producing high-frequency electrode used in thehigh-frequency plasma CVD system of the present invention will bedescribed with reference to FIGS. 3A and 3B. To simplify description,columnar rod-like electrodes are used as plasma-producing high-frequencyelectrodes 3 and hollow cylindrical dielectric members 4 are providedaround them. When plasma (not shown) is produced around the dielectric,a coaxial waveguide is formed in which each plasma-producinghigh-frequency electrode 3 serves as an internal conductor, the plasmaas an external conductor and the dielectric member 4 as a transmissionmedium. Each plasma-producing high-frequency electrode has a lengthwhich is ½ of wavelength λ in the coaxial waveguide at the frequency ofa high-frequency power used and present in the coaxial waveguide. Thehigh-frequency power generated by a high-frequency power source 11 isdivided into two parts through a matching circuit 10 so that thehigh-frequency power can be supplied in a good efficiency for loading;and is further supplied to each high-frequency electrode through eachauxiliary matching circuit 2 correspondingly to differences in matchingconditions, depending on differences in individuals of the respectivehigh-frequency electrodes 3. FIG. 3A also shows electric-field energydistribution of standing waves produced when a phase-adjusting circuit 1at an end of the left-side high-frequency electrode 3 is set as an openend and another phase-adjusting circuit 1 at an end of the right-sidehigh-frequency electrode 3 is set as a closed end [the ordinateindicates electrode position; and the abscissa, electric-field energy(arbitrary unit)]. If the energy supplied to plasma from theplasma-producing high-frequency electrode is proportional to theelectric-field energy of the high-frequency power, the uniformity ofplasma in the direction Z is dramatically improved when twohigh-frequency electrodes are used as shown in FIGS. 3A and 3B, comparedwith an instance where one high-frequency electrode is used. Inpractice, plasma is not an ideal coaxial external conductor but anabsorber having a fairly high-frequency power, and the diffusion or thelike of plasma must also be taken into account. Accordingly, moreuniform plasma can be formed by making appropriate phase adjustment, andalso effective is a method in which the plasma-producing high-frequencyelectrodes are provided in a larger number according to circumstances.As the phase-adjusting circuit which adjusts the phase, what is calledan LC circuit may be used, or, as a simple means, the electrodes mayeach be connected to a ground through a capacitor.

In an instance where the impedance of plasma changes greatly, it isbetter to use a variable capacitor or variable coil as in aphase-adjusting circuit shown in FIG. 3B. The phase-adjusting circuitshown in FIG. 3B is provided as a variable, series LC circuit.Alternatively, a parallel LC circuit may be used.

The amount of electric power applied to each high-frequency electrode isill-balanced depending on the value of impedance of the phase-adjustingcircuit in some cases. In such an instance, the plasma may be formednon-uniformly. When this occurs, the impedance of the auxiliary matchingcircuit 2 may be adjusted, whereby the proportion of the amount ofelectric power applied to each high-frequency electrode can be adjusted.As this auxiliary matching circuit 2, too, an LC circuit may be used.

In an instance where the impedance of plasma changes only a little,stationary LC circuits may be used in both the phase-adjusting circuitand the auxiliary matching circuit without any problem.

For the plasma-producing high-frequency electrode of the presentinvention, the high-frequency power used may preferably have a frequencyin the range of from 30 to 600 MHz.

In the plasma CVD system and the plasma CVD process which make use ofthe plasma-producing high-frequency electrodes of the present invention,constituted as described above, the plasma-producing high-frequencyelectrodes can form a uniform plasma, and hence a deposited film havingfilm quality and film thickness in a very good uniformity can be formed.This will be detailed below. FIGS. 4 and 5 illustrate a plasma CVDsystem as a preferred example of the plasma CVD system of the presentinvention. FIG. 5 is a cross-sectional view along the line 5—5 in FIG.4. In FIGS. 4 and 5, reference numeral 12 denotes a reactor.

Inside the reactor 12, one substrate holder 6A is placed at the centerof the reactor. Reference numeral denotes a cylindrical film-formingsubstrate provided on the substrate holder 6A.

The substrate holder 6A is provided internally with a heater 7 so thatthe cylindrical film-forming substrate 5 can be heated on the inside.The substrate holder 6A is also connected to a shaft (not shown)connected to a motor (not shown), so as to be set rotatable.

Reference numeral 6B denotes an auxiliary substrate holder for thecylindrical film-forming substrate 5. Reference numeral 3 denotes ahigh-frequency electrode (provided in plurality) to which ahigh-frequency power is applied and which is positioned at the center ofa plasma region. The high-frequency power is generated in ahigh-frequency power source 11, divided through a matching circuit 10,and supplied to one end of each high-frequency electrode 3 through anauxiliary matching circuit 2.

Each high-frequency electrode 3 is isolated from the discharge space viaa dielectric member 4 constituting a part of the reactor 12, and isgrounded through a phase-adjusting circuit 1 at an end on the sideopposite to the feeding point.

Gases are exhausted by a vacuum exhaust means 9 having a vacuum pump,through an exhaust pipe having an exhaust valve. Reference numeral 8denotes a material gas feed assemblage constituted of gas cylinders,mass-flow controllers, valves and so forth, which is connected to gasrelease pipes having a plurality of gas release holes, through a gasfeed pipe.

Plasma CVD using this system is carried out in the following way. Afterthe inside of the reactor 12 is evacuated to a high vacuum by means ofthe exhaust mechanism 9, reaction gases are fed into the reactor 12 fromthe gas feed means 8 through the gas feed pipes and gas release pipes,and its inside is kept at a predetermined pressure. In this state, ahigh-frequency power is supplied from the high-frequency power source11, after it is divided through the matching circuit 10, to eachhigh-frequency electrode 3 through the auxiliary matching circuit 2 tocause plasma to take place across the high-frequency electrodes and thecylindrical film-forming substrate 5. Thus, the reaction gases aredecomposed and excited by plasma to form a deposited film on thecylindrical film-forming substrate 5.

In the present invention, as a dielectric material used in thedielectric member 4, any known material may be selected. A materialhaving a small dielectric loss may preferably be used. Those having adielectric loss tangent of 0.01 or below are preferred, and those of0.001 or below are more preferred. As polymeric dielectric materials,polytetrafluoroethylene, polytrifluorochloroethylene, polyfluoroethylenepropylene and polyimide are preferred. As glass materials, quartz glassand borosilicate glass are preferred. As ceramic materials, preferredare boron nitride, silicon nitride, aluminum nitride, and ceramicscomposed chiefly of one or more element oxides among element oxides suchas aluminum oxide, magnesium oxide and silicon oxide.

In the present invention, the high-frequency electrode 3 may preferablyhave the shape of a rod such as a column, a cylinder or a polygonalpillar, or a long plate.

In the present invention, the high-frequency power generated from thehigh-frequency power source 11 may preferably have a frequency in therange of from 30 to 600 MHz, and more preferably from 60 to 300 MHz.

In the present invention, the system may be constituted as shown inFIGS. 6 and 7, in which a plurality of high-frequency electrodes 3 aredisposed around a cylindrical film-forming substrate 5 in such a waythat their one ends passes through the top wall of a reactor 12.

More specifically, in the system shown in FIGS. 6 and 7, high-frequencyelectrodes 3 each covered with a dielectric material 4 are provided ashigh-frequency power feed means around the film-forming substrate 5. Inthe present embodiment, four high-frequency power feed means areprovided at equal intervals. Gas release pipes 14 are provided betweenthese high-frequency power feed means.

In the present invention, the system may also be constituted as shown inFIG. 8, in which a plurality of cylindrical film-forming substrates 5are arranged on the same circumference.

The system shown in FIG. 8 has a high-frequency electrode 3 covered witha dielectric material 4, provided at the center of a reactor 12, and aplurality of high-frequency electrodes 3 provided on the outer side ofanother dielectric material 4 constituting the reactor 12, i.e., aroundthe outer side of the reactor 12. The film-forming substrates 5 are soprovided as to surround the high-frequency electrode 3 provided at thecenter of the reactor 12, and the gas release pipes 14 are so disposedas to be positioned between the respective film-forming substrates 5.The high-frequency electrodes 3 on the outer side of the reactor 12 arealso provided between the film-forming substrates 5 at positions withequal distance to the adjoining film-forming substrates 5. An earthshield 13 surrounds the outer-side high-frequency electrodes to preventthe high-frequency power from leaking out.

In the present invention, the system may also be constituted as shown inFIG. 9, in which a plurality of high-frequency electrodes 3 are disposedin parallel to a flat-plate film-forming substrate 5. With thisconstitution, a high-quality deposited film having a very uniform filmthickness and a homogeneous film quality can be formed on a large-areaflat-plate film-forming substrate at a high deposition rate.

In the present invention, the system may also be constituted as shown inFIG. 10, in which a plurality of high-frequency electrodes 3 aredisposed in parallel to a continuous sheet-like film-forming substrate 5which is wound off from a holding roll 15 at the time of film formationand wound up on a wind-up roll after film formation. With thisconstitution, a high-quality deposited film having a very uniform filmthickness and a homogeneous film quality can be formed on a large-areacontinuous sheet-like film-forming substrate at a high deposition rate.

In use of the plasma CVD system of the present invention, as the gasesused, known material gases contributory to film formation may be usedunder appropriate selection in accordance with the types of depositedfilms to be formed. For example, when a-Si (amorphous silicon) typedeposited films are formed, preferable material gases may includesilane, disilane, high disilane, and mixed gases of any of these. Whendifferent type deposited films are formed, they may include, e.g.,material gases such as germane, methane and ethylene, and mixed gases ofany of these. In either case, material gases for film formation may beintroduced into the reactor together with a carrier gas. The carrier gasmay include hydrogen gas and inert gases such as argon gas and heliumgas.

Property-improving gases for, e.g., controlling band gaps of depositedfilms may also be used. Such gases may include, e.g., gases containingnitrogen atoms, such as nitrogen and ammonia; gases containing oxygenatoms, such as oxygen, nitrogen dioxide and dinitrogen oxide;hydrocarbon gases such as methane, ethane, ethylene, acetylene andpropane; gaseous fluorine compounds such as silicon tetrafluoride,disilicon hexafluoride and germanium tetrafluoride; and mixed gases ofany of these.

Dopant gases may also be used for the doping of deposited films to beformed. Such dopant gases may include, e.g., gaseous diborane, boronfluoride, phosphine and phosphorus fluoride.

Substrate temperature at the time of the formation of deposited filmsmay be set appropriately. When amorphous silicon type deposited filmsare formed, the temperature may preferably be set at from 60° C. to 400°C., and more preferably from 100° C. to 350° C.

The phase adjustment of the high-frequency electrodes may preferably beso made that the phases of reflected waves on adjoining high-frequencyelectrodes differ from each other. In particular, the phase adjustmentmay preferably be so made as to compensate the strength or weakness ofelectric-field energy distribution around the adjoining high-frequencyelectrodes.

In the present invention, the plasma CVD system may be so constitutedthat the plasma-producing high-frequency electrode is provided with anauxiliary matching circuit on the power supply side of the electrode andthe high-frequency power branches through the auxiliary matching circuitfrom the high-frequency power source provided in a smaller number thanthe number of the plasma-producing high-frequency electrode, to controlthe high-frequency power supplied to each high-frequency electrode.

In such an instance, the auxiliary matching circuit may be constitutedof an LC circuit.

A dielectric member may preferably be provided between theplasma-producing high-frequency electrode and the space in which theplasma takes place.

The high-frequency electrode may be provided in plurality and aplurality of high-frequency electrodes may be arranged outside thereactor in which a film-forming substrate has been provided, and uprighton substantially the same circumference in such a way that thehigh-frequency electrodes surround the reactor; the reactor being formedof a dielectric member at least in part.

Alternatively, the high-frequency electrode may be provided in pluralityand a plurality of high-frequency electrodes may be arranged inside thereactor in which a film-forming substrate has been provided, and uprighton substantially the same circumference in such a way that thehigh-frequency electrodes surround the film-forming substrate.

Still alternatively, the high-frequency electrode may be provided inplurality and a plurality of high-frequency electrodes may be arrangedinside or outside the reactor in which a plurality of film-formingsubstrates have been provided, and upright on substantially the samecircumference in such a way that the high-frequency electrodes surroundthe film-forming substrates.

The film-forming substrate may preferably be so provided as to berotatable by means of a rotating mechanism. In this instance, thefilm-forming substrate may preferably have a cylindrical shape.

EXAMPLES

The present invention will be described below by giving Examples. Thepresent invention is by no means limited by these.

Example 1

A plasma CVD system used in the present Example is the onediagrammatically illustrated in FIGS. 4 and 5. FIG. 5 is across-sectional view along the line 5—5 in FIG. 4. As the high-frequencypower source 11, a power source able to output a power having afrequency in the range of from 13.56 MHz to 650 MHz was used. Thehigh-frequency electrodes 3 used has the shape of columns, which aredisposed outside the reactor 12 and are isolated from the dischargespace via a dielectric member 4 made of an alumina ceramic. Thehigh-frequency electrodes are each so set up as to have a feeding pointof the high-frequency power at its one end and be grounded through thephase-adjusting circuit 1 on the opposite-side end. As thephase-adjusting circuits 1, those able to adjust the reactance to groundwere used. In the present Example, with regard to high-frequencyelectrodes 3 shared by one set of opposing phase-adjusting circuitsamong four phase-adjusting circuits 1, these high-frequency electrodeswere short-circuited directly to grounds inside the reactor 12, andthose shared by the remaining opposing one set were not connected togrounds but set substantially as open ends of only the stray capacitancein the phase-adjusting circuits.

A cylindrical film-forming substrate made of aluminum and having adiameter of 108 mm, a length of 358 mm and a wall thickness of 5 mm wasset in the reactor 12 and film formation was tested while rotating thesubstrate. In this test, columnar electrodes made of aluminum, having adiameter of 20 mm and a length of 450 mm, were used as thehigh-frequency electrodes 3. For the evaluation of film quality, aCorning #7059 glass substrate on which a comb type electrode with gapsof 250 μm made of chromium had been vacuum-deposited was set as anelectrical property evaluation substrate (a substrate for evaluatingelectrical properties) on the surface of the cylindrical film-formingsubstrate over the length of 358 mm in its axial direction. The test wasmade in the following way.

First, the inside of the reactor 12 was evacuated by operating theexhaust mechanism 9, and the inside of the reactor 12 was adjusted to apressure of 1×10⁻⁶ Torr. Next, the substrate heater was electrified toheat the cylindrical film-forming substrate 5 and keep it at atemperature of 250° C. Then, films were formed in the followingprocedure: SiH₄ gas was fed from the material gas feed means 8 throughthe gas release pipes 14 into the reactor 12 at a flow rate of 500 sccm,and the inside of the reactor was adjusted to a pressure of 10 mm Torr.In this state, the high-frequency power was generated by thehigh-frequency power source 211 at frequencies within the range of from13.56 MHz to 650 MHz. The high-frequency power was divided into fourparts through the matching circuit 10, and then supplied equally to thehigh-frequency electrodes 3 through the auxiliary matching circuits 2.Here, as the high-frequency power source 11, a predeterminedhigh-frequency power source was used so as to provide the frequencieswithin the above range. The matching circuit 10 was adjustedappropriately in accordance with the frequencies of the high-frequencypower source. Thus, amorphous silicon films were formed on thecylindrical film-forming substrate 5 and the electrical propertyevaluation substrate described above.

With regard to the amorphous silicon films thus formed, their filmquality, film quality distribution, deposition rate and deposition ratedistribution were evaluated in the following manner.

The film quality and film quality distribution were evaluated bymeasuring light/dark conductivity ratio {(photoconductivity σp)/darkconductivity σd)} at 18 points at intervals of about 20 mm on theelectrical property evaluation substrate over its top end to its bottomend. Here, the photoconductivity σp is evaluated by conductivity at thetime of irradiation by light of a He—Ne laser (wavelength: 632.8 nm)with an intensity of 1 mW/cm². According to findings obtained by thepresent inventors from the manufacture of electrophotographicphotosensitive members, images which are worthy of practical use can beformed on electrophotographic photosensitive members manufactured underoptimum conditions on the basis of conditions under which depositedfilms having such quality that the light/dark conductivity ratiomeasured in the above manner is 10³ or more are obtainable. However,taking account of the trend in recent years toward higher contrast ofimages, it has become preferable for deposited films to have alight/dark conductivity ratio of 10⁴ or more, and it is foreseen that alight/dark conductivity ratio of 10⁵ or more is required in the nearfuture. From such a point of view, the value of the light/darkconductivity ratio was evaluated according to the following ranks.

AA: Light/dark conductivity ratio is 10⁵ or more, showing very good filmproperties.

A: Light/dark conductivity ratio is 10⁴ or more, showing good filmproperties.

B: Light/dark conductivity ratio is 10³ or more, and no problem inpractical use.

C: Light/dark conductivity ratio is less than 10³, and not suited forpractical use in some cases.

The deposition rate and deposition rate distribution were evaluated bymeasuring film thickness by the use of an eddy current film thicknessmeter (manufactured by Kett Kagaku Kenkyusho) at 18 points at intervalsof about 20 mm like the positions of measurement of the above light/darkconductivity ratio, on the a-Si film-formed cylindrical substrate in itsaxial direction. The deposition rate was calculated on the basis of thefilm thicknesses at 18 points, and an average value of the valuesobtained was regarded as an average deposition rate. The deposition ratedistribution was evaluated in the following way: With regard todeposition rate distribution in the axial direction, a differencebetween the maximum value and the minimum value in deposition rate atthe 18 points in the axial direction was determined, and its error wasdivided by the average deposition rate of 18 points to determinedeposition rate distribution {(maximum value−minimum value)/averagevalue}, which was expressed by percentage as deposition ratedistribution in the axial direction.

The results of evaluation of the light/dark conductivity ratio, averagedeposition rate and deposition rate distribution-of the film-formedsamples are shown in Table 1.

TABLE 1 Deposi- Average tion Power Light/dark conductivity ratio deposi-rate source Top side Bottom side tion distri- frequency (high-frequencypower (phase-adjusting rate bution (MHz) feeding side) ← Middle portion→ circuit side) (nm/s) (%) 30 A   A A A A A A A A A A A A A A A A   A2.0 3 60 AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA 4.0 4 100AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA 6.4 4 200 AA AA AAAA AA AA AA AA AA AA AA AA AA AA AA AA AA AA 7.1 4 300 AA AA AA AA AA AAAA AA AA AA AA AA AA AA AA AA AA AA 5.6 5 400 A   A A A A A A A A A A AA A A A A   A 2.8 6 500 A   A A A A A A A A A A A A A A A A   A 2.4 7600 A   A A A A A A A A A A A A A A A A   A 2.0 7

In the case of 13.56 MHz, no discharge took place at 10 mTorr and hencethe evaluation was impossible.

With regard to samples on which films were formed using high-frequencypower having a frequency of 30 MHz, the light/dark conductivity ratiowas within the range of from 1×10⁴ to 3×10⁴ in all the samples, showinggood film properties “A” (Table 1). The average deposition rate was 2.0nm/second and the deposition rate distribution was 3%.

With regard to samples on which films were formed using high-frequencypower having a frequency of from 60 MHz to 300 MHz, the light/darkconductivity ratio was within the range of from 1×10⁵ to 5×10⁵ in allthe samples, showing very good film properties “AA” (Table 1). Theaverage deposition rate was from 4.0 to 7.1 nm/second and the depositionrate distribution was from 4 to 5%.

With regard to samples on which films were formed using high-frequencypower having a frequency of from 400 MHz to 600 MHz, the light/darkconductivity ratio was within the range of from 5×10⁴ to 8×10⁴, showinggood film properties “A” (Table 1). The average deposition rate was from2.0 to 2.8 nm/second and the deposition rate distribution was from 6 to7%.

In the case of 650 MHz, the discharge was too unstable to form depositedfilms.

Thus, in the present Example, amorphous silicon films having goodlight/dark conductivity ratio and good average deposition rate anddeposition rate distribution are obtained under discharge frequencyconditions of from 30 MHz to 600 MHz, and especially superior amorphoussilicon films were obtained at frequencies of from 60 MHz to 300 MHz.

Comparative Example 1

A system in which all the phase-adjusting circuits 1 were detached andthe ends of all the cathode electrodes (high-frequency electrodes) 3were set as open ends was examined under the same conditions as inExample 1, and evaluation was made in the same manner as in Example 1.The results of evaluation are shown in Table 2. Compared with theresults of Example 1 shown in Table 1, the light/dark conductivity ratiois greatly low and the deposition rate distribution is greatlynon-uniform, at the all discharge frequencies.

TABLE 2 Power Light/dark conductivity ratio Average Deposition sourceTop side Bottom side deposition rate frequency (high-frequency power(phase-adjusting rate distribu- (MHz) feeding side) ← Middle portion →circuit side) (nm/s) tion (%) 30 B   B C C C B B B B B B B A A A A A   A1.8 11 60 AA A A B B C C B A A AA AA AA AA AA AA AA AA 3.3 18 100 AA AAAA AA A A B C C B A AA AA AA AA AA AA AA 5.7 24 200 AA AA AA AA AA A A BC C C B A AA AA AA AA AA 6.5 29 300 A   A AA AA AA AA AA AA A B C C C BA AA AA AA 4.8 32 400 A   A B C C B A A A A A C C C A A A   A 2.3 38 500A   A B B C C B A A A A A C C C B A   A 1.9 40 600 A   C C A A B C C C BA A A C C C B   A 1.4 44

Example 2

Using the system shown in FIGS. 4 and 5, electrophotographicphotosensitive members were produced under the conditions where thevalue of a light/dark conductivity ratio of 10⁵ or more was obtained inExample 1, i.e., under conditions of power source frequencies 60 MHz,100 MHz, 200 MHz and 300 MHz each. As the phase-adjusting circuits 1,the same ones as those used in Example 1 were used. The high-frequencyelectrodes 3 on their side opposite to the feeding points were set inthe same manner as in Example 1. The electrophotographic photosensitivemembers were each produced by forming a charge injection blocking layer,a photoconductive layer and a surface protective layer in this order ona cylindrical film-forming substrate made of aluminum, underfilm-forming conditions shown in Table 3.

On the samples obtained under the respective conditions of power sourcefrequencies, their chargeability, image density and faulty images wereevaluated. As the result, all the electrophotographic photosensitivemembers showed very good results on these evaluation items over thewhole areas of the electrophotographic photosensitive members. As wasseen from these results, all the electrophotographic photosensitivemembers had superior electrophotographic performances.

TABLE 3 Electrophotographic photosensitive member layers Film-formingconditions Surface protective layer: Gas flow rate: SiH₄ 100 sccm H₂ 100sccm CH₄ 500 sccm Power applied: 800 W Reaction pressure: 10 mTorr Filmthickness: 1 μm Photoconductive layer: Gas flow rate: SiH₄ 500 sccm H₂500 sccm Power applied: 1,000 W Reaction pressure: 10 mTorr Filmthickness: 30 μm Charge injection blocking layer: Gas flow rate: SiH₄400 sccm H₂ 400 sccm NO 500 sccm B₂H₆ 2,000 ppm (based on SiH₄ flowrate) Power applied: 800 W Reaction pressure: 10 mTorr Film thickness: 2μm

Example 3

Using the system shown in FIGS. 6 and 7, a cylindrical film-formingsubstrate 5 made of aluminum and having a diameter of 108 mm, a lengthof 358 mm and a wall thickness of 5 mm was set in the reactor 12 to formfilms. As the high-frequency electrodes, the same ones as those inExample 1 were set in the reactor, and those covered with dielectricmembers 4 were used. Four high-frequency electrodes were disposed in thereactor as shown in FIG. 7. Using a high-frequency power source able toapply a power having a frequency of 100 MHz, an amorphous silicon filmwas formed on the cylindrical film-forming substrate under the samefilm-forming conditions as in Example 1. The light/dark conductivityratio, deposition rate and deposition rate distribution were evaluatedin the same manner as in Example 1. The high-frequency electrodes 3 ontheir side opposite to the feeding points were set in the same manner asin Example 1.

As the result, the light/dark conductivity ratio was from 1×10⁵ to 3×10⁵at all positions, the average deposition rate was 6.7 nm/second and thedeposition rate distribution was 4%. Thus, an amorphous silicon filmhaving uniform and good properties was obtained.

Example 4

Electrophotographic photosensitive members were produced under the samesystem constitution as used in Example 3.

The electrophotographic photosensitive members were each produced byforming a charge injection blocking layer, a photoconductive layer and asurface protective layer in this order on a cylindrical film-formingsubstrate made of aluminum, in the same manner as in Example 2 underfilm-forming conditions shown in Table 3. On the samples obtained, theirchargeability, image density and faulty images were evaluated. As theresult, all the electrophotographic photosensitive members also showedvery good results on these evaluation items over the whole areas of theelectrophotographic photosensitive members. As was seen from theseresults, all the electrophotographic photosensitive members had superiorelectrophotographic performances.

Example 5

Using the system shown in FIG. 8, cylindrical film-forming substrates 5each made of aluminum and having a diameter of 108 mm, a length of 358mm and a wall thickness of 5 mm were set in the reactor 12 to formfilms. To set up the high-frequency electrodes 3, the same ones as thosein Example 1 were used as seven high-frequency electrodes 3, six ofwhich were disposed outside the reactor 12 and one of which was disposedat the center of the reactor, in the manner as shown in FIG. 8. Thereactor 12 is constituted of a dielectric member 4 in part, and is sodesigned that the high-frequency power from the high-frequencyelectrodes disposed outside the reactor can be fed into the reactor 12.The high-frequency electrode 3 inserted to the center of the reactor iscovered with a dielectric member 4. The phase-adjusting circuit (notshown) connected to the center high-frequency electrode isshort-circuited to a ground and the phase-adjusting circuits (not shown)connected to the surrounding six high-frequency electrodes 3 areconnected to grounds through capacitors each having inside anelectrostatic capacity of 20 pF. As the capacitors, any types such asceramic capacitors and vacuum capacitors may be used. A high-frequencypower source able to apply a power having a frequency of 100 MHz wasused. Films were formed under conditions of a high-frequency power of 4kW, an SiH₄ flow rate of 1,500 cc, a film-forming pressure of 10 mTorrand a substrate temperature of 250° C., and amorphous silicon films wereformed on the six cylindrical film-forming substrates. The light/darkconductivity ratio, deposition rate and deposition rate distributionwere evaluated in the same manner as in Example 1.

As the result, the light/dark conductivity ratio was from 1×10⁵ to 3×10⁵at all positions, the average deposition rate was 6.2 nm/second and thedeposition rate distribution was 5%. Thus, amorphous silicon filmshaving uniform and good properties were obtained.

Example 6

Electrophotographic photosensitive members were produced under the samesystem constitution as used in Example 5.

The electrophotographic photosensitive members were produced by forminga charge injection blocking layer, a photoconductive layer and a surfaceprotective layer in this order on each of the six cylindricalfilm-forming substrates made of aluminum, under film-forming conditionsshown in Table 4. On the samples obtained, their chargeability, imagedensity and faulty images were evaluated. As the result, all theelectrophotographic photosensitive members also showed very good resultson these evaluation items over the whole areas of theelectrophotographic photosensitive members. As was seen from theseresults, all the electrophotographic photosensitive members had superiorelectrophotographic performances.

TABLE 4 Electrophotographic photosensitive member layers Film-formingconditions Surface protective layer: Gas flow rate: SiH₄ 300 sccm H₂ 300sccm CH₄ 1,500 sccm Power applied: 3,000 W Reaction pressure: 5 mTorrFilm thickness: 1 μm Photoconductive layer: Gas flow rate: SiH₄ 1,500sccm H₂ 1,500 sccm Power applied: 4,000 W Reaction pressure: 10 mTorrFilm thickness: 30 μm Charge injection blocking layer: Gas flow rate:SiH₄ 1,000 sccm H₂ 1,000 sccm NO 1,200 sccm B₂H₆ 2,000 ppm (based onSiH₄ flow rate) Power applied: 2,500 W Reaction pressure: 10 mTorr Filmthickness: 2 μm

Example 7

Using the system shown in FIG. 9, a flat-plate film-forming substrate 5made of glass and having a length of 500 mm, a width of 500 mm and athickness of 1 mm was set in the reactor to form films. Fourhigh-frequency electrodes 3 were disposed in the manner as shown in FIG.9. One ends of the high-frequency electrodes were put together throughthe auxiliary matching circuits 2 and thereafter, through the matchingcircuit 10, connected to a high-frequency power source 11 having anoscillation at a frequency of 200 MHz. On the other ends of thehigh-frequency electrodes, the phases of reflected power are adjusted bythe phase-adjusting circuits. This time, four phase-adjusting circuitswere set as an open end, a short-circuit end, an open end and ashort-circuit end in this order.

An amorphous silicon film was formed on the flat-plate film-formingsubstrate under film-forming conditions of a high-frequency power of 4kW, an SiH₄ flow rate of 1,000 sccm, a film-forming pressure of 10 mTorrand a substrate temperature of 250° C., and the deposition rate anddeposition rate distribution were evaluated in the following manner. Onthe flat-plate substrate on which the amorphous silicon film was formed,lines were drawn in its longitudinal direction at intervals of about 30mm, and lines were also drawn in the lateral direction at intervals ofabout 30 mm, where, at its 256 points of intersection, film thicknesswas measured and deposition rate was calculated at each position ofmeasurement in the same manner as in Example 1. An average value of thevalues obtained was regarded as an average deposition rate. The averagedeposition rate thus obtained was 7.4 nm/second. With regard to thedeposition rate distribution, a difference between the maximum value andthe minimum value in deposition rate at the 256 points of measurementwas determined. Its error was divided by the average deposition rate,and the value obtained was expressed by percentage as deposition ratedistribution. The deposition rate distribution thus obtained was 7%. Thelight/dark conductivity ratio was also evaluated in the same manner,which was found to be from 1×10⁵ to 3×10⁵ at all points of measurement.Thus, an amorphous silicon film having uniform and good properties wasobtained.

Example 8

Using the system shown in FIG. 10, a continuous sheet-like substrate 5made of stainless steel and having a width of 500 mm and a thickness of0.1 mm was set in the reactor to form films while winding off thesubstrate from the holding roll 15 and winding up it on the wind-up roll16. The high-frequency electrodes were set up using long-platehigh-frequency electrodes 3 made of aluminum and having a cross sectionof 40 mm×10 mm size and a length of 600 mm, each covered with a 5 mmthick dielectric member 4 made of an alumina ceramic, and two plate-likehigh-frequency electrodes were disposed in the reactor. Using ahigh-frequency power source able to output a power having a frequency of300 MHz, an amorphous silicon film was formed on the continuoussheet-like substrate under film-forming conditions of a high-frequencypower of 2 kW, an SiH₄ flow rate of 750 cc, a film-forming pressure of10 mTorr and a substrate temperature of 250° C. The phase-adjustingcircuits 1 connected to one ends of the high-frequency electrodes 3 wereset as an open end and a short-circuit end, and the phases of reflectedpower were adjusted by them.

The continuous sheet-like substrate was cut in a length of 500 mm, andthe light/dark conductivity ratio, deposition rate and deposition ratedistribution were evaluated in the same manner as in Example 6. Thelight/dark conductivity ratio was from 1×10⁵ to 3×10⁵ at all points ofmeasurement, the average deposition rate was 4.5 nm/second and thedeposition rate distribution was 5%. Thus, an amorphous silicon filmhaving uniform and good properties was obtained.

As described above, the present invention is so constituted that thephase-adjusting circuit which adjusts the phase of reflected power isconnected at an end on the side opposite to the feeding point of theplasma-producing high-frequency electrode. Hence, high-quality depositedfilms having a very uniform film thickness and a homogeneous filmquality can be formed at a high rate on large-area substrates havingvarious shapes, i.e., on cylindrical film-forming substrates, flat-platesubstrates and continuous sheet-like substrates.

Thus, according to the present invention, large-area and high-qualitysemiconductor devices can be manufactured efficiently, in particular,large-area deposited films having superior electrophotographicperformances can be mass-produced stably.

Incidentally, the adjustment of phase by the phase-adjusting circuitconnected to the side opposite to the feeding point is not limited toopen setting or short-circuit setting. The circuit may be set in anydesired state by adjusting, e.g., a reactance to control the standingwaves.

What is claimed is:
 1. A plasma CVD system comprising a reactor theinside of which can be evacuated, a substrate holding means provided inthe reactor, a material gas feed means for feeding into the reactor amaterial gas for plasma CVD, a high-frequency power supply means forsupplying to a plasma-producing high-frequency electrode ahigh-frequency power having an oscillation frequency in the range offrom 30 MHz to 600 MHz, generated by a high-frequency power source, andan exhaust means for exhausting a gas remaining in the reactor after thereaction; the high-frequency power generated in the high-frequency powersource being supplied to the plasma-producing high-frequency electrodeto cause a plasma to take place across a substrate held by the substrateholding means and the plasma-producing high-frequency electrode to forma deposited film on the substrate; wherein, a phase-adjusting circuitfor adjusting the phase of reflected power is connected to theplasma-producing high-frequency electrode at its end portion on theopposite side of a feeding point at which the high-frequency power issupplied to the plasma-producing high-frequency electrode.
 2. The plasmaCVD system according to claim 1, wherein the phase-adjusting circuitcomprises an LC circuit.
 3. The plasma CVD system according to claim 1,wherein the plasma-producing high-frequency electrode is provided withan auxiliary matching circuit on the power supply side of the electrodeand the high-frequency power branches through the auxiliary matchingcircuit from the high-frequency power source provided in a smallernumber than the number of the plasma-producing high-frequency electrode,to control the high-frequency power supplied to each high-frequencyelectrode.
 4. The plasma CVD system according to claim 3, wherein theauxiliary matching circuit comprises an LC circuit.
 5. The plasma CVDsystem according to claim 1, wherein the high-frequency power has anoscillation frequency in the range of from 60 MHz to 300 MHz.
 6. Theplasma CVD system according to claim 1, wherein a dielectric member isprovided between the plasma-producing high-frequency electrode and thespace in which the plasma is produced.
 7. The plasma CVD systemaccording to claim 1, wherein the high-frequency electrode is providedin plurality and the plurality of high-frequency electrodes are arrangedoutside the reactor in such a way that the high-frequency electrodessurround the reactor, the reactor being formed of a dielectric member atleast in part.
 8. The plasma CVD system according to claim 1, whereinthe high-frequency electrode is provided in plurality and the pluralityof high-frequency electrodes are arranged inside the reactor in such away that the high-frequency electrodes surround the film-formingsubstrate disposed therein.
 9. The plasma CVD system according to claim1, wherein the high-frequency electrode is provided in plurality and theplurality of high-frequency electrodes are arranged inside or outsidethe reactor in such a way that the high-frequency electrodes surroundthe film-forming substrate disposed therein.
 10. The plasma CVD systemaccording to claim 1, which further comprises a rotating mechanism forrotating the film-forming substrate.
 11. The plasma CVD system accordingto claim 1, wherein the substrate comprises a flat-plate substrate, andthe high-frequency electrode is provided in plurality so as to bearranged in parallel to the flat-plate substrate disposed.
 12. Theplasma CVD system according to claim 1, wherein the substrate comprisesa continuous sheet-like substrate which is wound off from a holding rollat the time of film formation and is wound up on a wind-up roll afterfilm formation, and the plasma-producing high-frequency electrode isprovided in plurality so as to be arranged in parallel to the sheet-likesubstrate to be fed.
 13. The plasma CVD system according to claim 1,wherein the plasma-producing high-frequency electrode has a rod-like orplate-like conductive member.
 14. The plasma CVD system according toclaim 1, wherein the plasma-producing high-frequency electrode isprovided in plurality, and the phase-adjusting circuit is provided toeach plasma-producing high-frequency electrode.
 15. The plasma CVDsystem according to claim 1, which further comprises a plasma-producinghigh-frequency electrode connected directly to a ground.